Over the last four seasons, the Golden State Warriors have owned the third quarter. Any game, no matter what the score at halftime, has seemed to tilt their way as soon as the second half begins.

The Boston Celtics turned that notion on its head Thursday night, completely taking over in the third against the Warriors. And after they made the defending champions sweat, they outfought them in the fourth quarter for a shocking 92-88 victory.

It was a strong enough performance by the Celtics that Stephen Curry was asked after the game about potentially returning to Boston for the N.B.A. Finals. Curry noted that the Celtics would have to get past Cleveland first but was far from dismissive.

“I hear the weather is great here in June,” he said, drawing a big laugh from the assembled crowd of reporters.

It was a game of highs and lows for Boston. Jaylen Brown had multiple highlight-reel dunks, Al Horford was quietly excellent, and the team reeled off an outrageous 19-0 run in the third quarter. But for much of the night they were struggling to overcome a terrible start from both Kyrie Irving and Jayson Tatum. In the end, the early struggles by those two starters proved inconsequential, as Boston’s winning streak reached 14 games thanks in part to Irving and Tatum being right in the middle of the action in the game’s closing moments.

While Irving had a game far below his standards — he scored just 16 points on 4 of 16 shooting and ditched his protective face mask in the second half — he hit two crucial free throws to give the Celtics the lead with 14 seconds left in the game. Then Tatum, who had been almost invisible in the first half, iced Golden State with two more free throws for a 4-point lead that Boston would not surrender. The duo scored 18 of their 28 points in the final period.

Both teams put together big scoring runs throughout the game, but the biggest came from Boston in the third quarter. Golden State started the period with a 5-point lead, and with 4 minutes 59 seconds remaining in the period, that had grown to 17. But Boston, led by Horford and Brown, scored the next 19 points to seize the lead, taking advantage of the officials’ allowing a great deal of contact defensively to force the Warriors into numerous bad shots.

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Jaylen Brown repeatedly frustrated the Warriors on both ends of the court, finishing his night with 22 points and 7 rebounds.CreditMichael Dwyer/Associated Press

The score was tied at 68-68 to start the fourth, and it proved to be a nail-biter to the finish — Klay Thompson’s 3-pointer with 1:22 left in the game was the only non-free throw scored in the game’s final 2:30. But the Celtics, as they have all season, took care of business late, outscoring the Warriors in the period by 24-20.

The Celtics finished with 38 free throw attempts compared to 19 for Golden State, and Draymond Green, the Warriors’ forward, chief defender and unofficial spokesman, risked a fine by embedding some criticism of the officiating in his dismissal of the suggestion that Irving led Boston to a dramatic win.

“He got to the free throw line a lot,” Green said. “That was it. He didn’t make no shots. He got to the free throw line. Whether they were fouls or not is another discussion.”

If there was a breakout star of the game, it was Brown, the second-year guard, who had 22 points and seven rebounds, showing tenacity on both ends of the court. He fired up the Boston crowd with a few big dunks and seemed to repeatedly frustrate Golden State’s star backcourt of Curry and Thompson. Curry, who was in foul trouble for much of the game, finished with just 9 points on 3 of 14 shooting.

Brown’s performance took on some added significance when he revealed after the game that he nearly did not play because his best friend from high school, Trevin Steede, had died on Wednesday.

“I knew coming in today that he wanted me to play,” Brown told reporters. “It was hard getting my thoughts together, but after talking to his mom and his family it inspired me to come out and play.”

While Brown gave them fits all night, Warriors Coach Steve Kerr cited Curry’s foul trouble as one of the biggest reasons for his team’s defeat, but praised the defensive work that helped keep the score so low. But Boston’s defenders were better, holding the league’s top-scoring offense to a season-low 88 points.

The road loss ended the Warriors’ winning streak at seven games, poking a bit of a hole in the argument that the Celtics’ long winning streak has merely been a result of weak competition. Despite the absence of Gordon Hayward, who has been out since the first quarter of the season opener, they have somewhat narrowed the gap that exists between their squad and Golden State in terms of overall excellence.

Golden State’s four-game road trip will continue on Saturday as they face Joel Embiid and the Philadelphia 76ers, but it would be worth circling Jan. 27 on the calendar, as that is when the Warriors will get their chance at revenge against the Celtics in Oakland.

A version of this article appears in print on , on Page B11 of the New York edition with the headline: Pro Basketball; Celtics Beat Warriors, for 14th Straight. Order Reprints | Today’s Paper | Subscribe